This invention relates to a scientific instrument for spectroscopy and in particular to a scientific instrument for spectroscopy suitably used for the ultraviolet and visible region.
In the field of the spectroscopical analysis a wide wavelength region extending from ultraviolet to visible light is used. For the light source used in an instrument by which qualitative and quantitative analysis is effected while measuring absorption of light by material, among various scientific instruments for spectroscopy, it is particularly important that fluctuations in light intensity with the time are small. However, there are in practice no single light sources having an emission spectrum extending from the ultraviolet to the visible region and small fluctuations in light intensity. As a light source having an emission spectrum in these regions there is known a xenon short arc lamp, but it is not used in practice, because its fluctuations in light intensity with the time are great. On the contrary, as light source having small fluctuations in light intensity with the time, there are known a deuterium discharge lamp and a tungsten lamp. The emission spectrum of the deuterium discharge lamp is strong in the ultraviolet region, but weak in the visible region and on the other hand, that of the tungsten lamp is strong in the visible region but weak in the ultraviolet region. For this reason these lamps cannot cover alone the wide wavelength region extending from the ultraviolet to the visible light. Consequently, in a prior art device, a construction is adopted, by which the light path is changed mechanically by means of a mirror, etc. so that as the light source a deuterium discharge lamp is used for the short wavelength side and a tungsten lamp for the long wavelength side. Therefore, it had disadvantages that the mechanism is complicated, further that since the two light paths are not coincide with each other at the wavelength, at which that light sources are changed over, measured absorption spectrum changes stepwise there, etc.
Moreover a lamp, in which a deuterium discharge lamp and a tungsten lamp are incorporated in one body so that it can be used as a light source covering the wavelength region extending from the ultraviolet to the visible light, is described in No. JP-A-59-215654. However, since the emitting point of the deuterium discharge lamp and that of the tungsten lamp are different in this lamp, it has difficulty in regulating the two emitting points on a same light axis, further that two power supplier are necessary for the deuterium discharge lamp and for the tungsten lamp, etc.
As described above, according to the prior art techniques, since there were no suitable light sources, there were problems that the instrument was complicated and expensive, that measurement result was wanting in reliability, etc.